Today's Message Index:
----------------------
1. 05:06 AM - Re: CJ-6A comm antenna (Noplugs)
2. 05:31 AM - Re: Re: CJ-6A comm antenna (cjpilot710@aol.com)
3. 07:43 AM - Re: Re: CJ-6A comm antenna (Warren Hill)
4. 07:43 AM - Re: Re: CJ-6A comm antenna (Warren Hill)
5. 08:23 AM - Re: Need Mechanic N.Calif (Bill1200)
6. 09:19 AM - Re: Re: CJ-6A comm antenna (T A LEWIS)
7. 09:45 AM - Re: Re: CJ-6A comm antenna (cjpilot710@aol.com)
8. 10:04 AM - Re: Re: CJ-6A comm antenna (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
9. 10:31 AM - Re: CJ-6A comm antenna (Noplugs)
10. 12:10 PM - Re: Re: CJ-6A comm antenna (Warren Hill)
11. 02:12 PM - Re: Re: CJ-6A comm antenna (Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E)
12. 03:40 PM - Re: CJ-6A comm antenna (Marcus Bates)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
I have everything you need. I am restoring my CJ and getting rid of all the original
comm equipment and radio nav gear. All the coax is un-cut, the Antenna is
in good shape and the insulator is good to.
Thanks
Mike
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=262237#262237
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time,
qas44n@yahoo.com writes:
I wish I had known that a week ago. I just bought and installed a new
one. :-(
Anyway my local radio shop, told me that the Chinese antenna was a "little
to long" for the frequency band and may have been the reason some guys were
complaining of not hearing me to well over my Terra radios.
Jim
--> Yak-List message posted by: "Noplugs" <qas44n@yahoo.com>
I have everything you need. I am restoring my CJ and getting rid of all
the original comm equipment and radio nav gear. All the coax is un-cut, the
Antenna is in good shape and the insulator is good to.
Thanks
Mike
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=262237#262237
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
Jim,
I'm sure that your radio guys mean well, but they're not be seeing the
whole picture.
The efficiency of a vertical radiator at VHF frequencies not only
depends on its length (which determines the resonant frequency), but
also the efficient transfer of power through the coax (RG-58 pretty
lossy at 120 MHz), the transfer of power from the coax to the antenna
(a non-refurbished Chinese PL-259 is low quality and an American one
doesn't mate well to the Chinese SO-239), the counterpoise (kinda like
a ground), it's angle (which influences the input impedance) and the
counterpoise conductivity (anodized aluminum is a poor choice).
With high quality coax (not the stuff that's normally available), a
copper counterpoise and the Chinese SO-239 / PL-259 connectors
refurbished, the resonant frequency for my CJ comm antenna is 124.82
MHz, around the center of the aviation band. The frequency range for
an acceptable SWR (standing wave ratio, which determines how much
transmitted power gets reflected back to the radio) is much broader
than any aviation wire antenna I've seen. This is because the width of
the radiating element also influences its bandwidth.
My take... getting this to work properly is simply way too much work
for a standard repair station with guys who are mostly trained to
"assemble and test." I've been working with antennas for more than 40
years. Set up correctly, the CJ comm antenna works great.
All the best,
Warren Hill
Mesa, Arizona
On Sep 9, 2009, at 5:27 AM, cjpilot710@aol.com wrote:
> In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time, qas44n@yahoo.com
> writes:
>
> I wish I had known that a week ago. I just bought and installed a
> new one. :-(
>
> Anyway my local radio shop, told me that the Chinese antenna was a
> "little to long" for the frequency band and may have been the reason
> some guys were complaining of not hearing me to well over my Terra
> radios.
>
> Jim
>
>
> I have everything you need. I am restoring my CJ and getting rid of
> all the original comm equipment and radio nav gear. All the coax is
> un-cut, the Antenna is in good shape and the insulator is good to.
>
> Thanks
> Mike
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?
> p=262237#262237==============================================
> ================================================ -
> MATRONICS WEB FORUMS
> ================================================ - List
> Contribution Web Site sp;
> ==================================================
>
>
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
Mike,
Wonderful. Can I have your phone number off line?
Warren Hill
Mesa, Arizona
On Sep 9, 2009, at 5:04 AM, Noplugs wrote:
>
> I have everything you need. I am restoring my CJ and getting rid of
> all the original comm equipment and radio nav gear. All the coax is
> un-cut, the Antenna is in good shape and the insulator is good to.
>
> Thanks
> Mike
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=262237#262237
>
>
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Need Mechanic N.Calif |
Thanks Jim, Red Bluff is really close. Had no idea they had someone there that
could work on russian stuff.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=262273#262273
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
I use the original commie antenna on my cj aqnd it works great.
Terry Lewis
----- Original Message ----
From: Warren Hill <k7wx@earthlink.net>
Sent: Wednesday, September 9, 2009 10:23:49 AM
Subject: Re: Yak-List: Re: CJ-6A comm antenna
Jim,
I'm sure that your radio guys mean well, but they're not be seeing the whole picture.
The efficiency of a vertical radiator at VHF frequencies not only depends on its
length (which determines the resonant frequency), but also the efficient transfer
of power through the coax (RG-58 pretty lossy at 120 MHz), the transfer
of power from the coax to the antenna (a non-refurbished Chinese PL-259 is low
quality and an American one doesn't mate well to the Chinese SO-239), the counterpoise
(kinda like a ground), it's angle (which influences the input impedance)
and the counterpoise conductivity (anodized aluminum is a poor choice).
With high quality coax (not the stuff that's normally available), a copper counterpoise
and the Chinese SO-239 / PL-259 connectors refurbished, the resonant
frequency for my CJ comm antenna is 124.82 MHz, around the center of the aviation
band. The frequency range for an acceptable SWR (standing wave ratio, which
determines how much transmitted power gets reflected back to the radio) is much
broader than any aviation wire antenna I've seen. This is because the width
of the radiating element also influences its bandwidth.
My take... getting this to work properly is simply way too much work for a standard
repair station with guys who are mostly trained to "assemble and test." I've
been working with antennas for more than 40 years. Set up correctly, the CJ
comm antenna works great.
All the best,
Warren Hill
Mesa, Arizona
On Sep 9, 2009, at 5:27 AM, cjpilot710@aol.com wrote:
> In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time, qas44n@yahoo.com
writes:
>
> I wish I had known that a week ago. I just bought and installed a new one. :-(
>
> Anyway my local radio shop, told me that the Chinese antenna was a "little to
long" for the frequency band and may have been the reason some guys were complaining
of not hearing me to well over my Terra radios.
>
> Jim
>
>
> I have everything you need. I am restoring my CJ and getting rid of all the original
comm equipment and radio nav gear. All the coax is un-cut, the Antenna
is in good shape and the insulator is good to.
>
> Thanks
> Mike
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=262237#262237==============================================
> ================================================ - MATRONICS WEB FORUMS
================================================ - List Contribution Web
Site sp; ==================================================
>
>
>
>
>
>
>
>
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
In a message dated 9/9/2009 10:44:24 A.M. Eastern Daylight Time,
k7wx@earthlink.net writes:
Warren,
Boy I am glad someone understands this magic stuff about antenna's. For
some 50 plus years, my total knowledge was "press the button and talk".
Honest. I was so happy when we got 'single side band' our HF radios, so that
I didn't have to listen to hour on hour of static, listening to every
transmission. I had not idea what "single side band" was (nor do I need to
now!!!!) but it was great magic.
Nice thing about this list, even an old dog can appreciate the smart guys
who understand the details of what appears to be a simple device.
Thanks.
Jim "Pappy" Goolsby
--> Yak-List message posted by: Warren Hill <k7wx@earthlink.net>
Jim,
I'm sure that your radio guys mean well, but they're not be seeing the
whole picture.
The efficiency of a vertical radiator at VHF frequencies not only
depends on its length (which determines the resonant frequency), but
also the efficient transfer of power through the coax (RG-58 pretty
lossy at 120 MHz), the transfer of power from the coax to the antenna
(a non-refurbished Chinese PL-259 is low quality and an American one
doesn't mate well to the Chinese SO-239), the counterpoise (kinda like
a ground), it's angle (which influences the input impedance) and the
counterpoise conductivity (anodized aluminum is a poor choice).
With high quality coax (not the stuff that's normally available), a
copper counterpoise and the Chinese SO-239 / PL-259 connectors
refurbished, the resonant frequency for my CJ comm antenna is 124.82
MHz, around the center of the aviation band. The frequency range for
an acceptable SWR (standing wave ratio, which determines how much
transmitted power gets reflected back to the radio) is much broader
than any aviation wire antenna I've seen. This is because the width of
the radiating element also influences its bandwidth.
My take... getting this to work properly is simply way too much work
for a standard repair station with guys who are mostly trained to
"assemble and test." I've been working with antennas for more than 40
years. Set up correctly, the CJ comm antenna works great.
All the best,
Warren Hill
Mesa, Arizona
On Sep 9, 2009, at 5:27 AM, cjpilot710@aol.com wrote:
> In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time,
qas44n@yahoo.com
> writes:
>
> I wish I had known that a week ago. I just bought and installed a
> new one. :-(
>
> Anyway my local radio shop, told me that the Chinese antenna was a
> "little to long" for the frequency band and may have been the reason
> some guys were complaining of not hearing me to well over my Terra
> radios.
>
> Jim
>
>
> I have everything you need. I am restoring my CJ and getting rid of
> all the original comm equipment and radio nav gear. All the coax is
> un-cut, the Antenna is in good shape and the insulator is good to.
>
> Thanks
> Mike
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?
> p=262237#262237==============================================
> ================================================ -
> MATRONICS WEB FORUMS
> ================================================ - List
> Contribution Web Site sp;
> ==================================================
>
>
Message 8
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
Warren, concur on most of your comments. Obviously a fellow ham radio
operator. Just some additional thoughts.
The best replacement coax for RG-58 (with cost considerations) would
likely be RG-142B/U ... Double shielded, silver coated, solid center
conductor Teflon dielectric. Higher velocity factor than most others,
(less loss) but somewhat less flexible. Failing that, RG-223. Same
stuff, but with a polypropylene dielectric instead of Teflon. Standard
.66 Vp. RG-142 is good up to over 1 GHz for short runs.
I do not know CJ's at all, and possibly a better counterpoise is
necessary, however I respectfully disagree that anodized aluminum is a
poor choice. Anodized aluminum is used as a counterpoise on every
commercial and most civilian aircraft in the world. Anodized aluminum
is used to construct a wide variety of HF and UHF antennas (WA3JPY
Warren :-) Concur that copper is a better choice, and silver would be
even better than copper, but in the real world, I honestly offer that
the difference in antenna performance between aluminum and copper is
extremely small.
The main problem when using anodized aluminum as the counterpoise to the
1/4 wavelength vertical is that you might not get a good electrical bond
TO the actual aluminum because of the alodine used to cause the
artificial corrosion method that is part of the anodizing process. This
is why current military aircraft designs have gone to using AVDECK seals
between the base of the antenna and the aircraft skin.
Point being is that if you take care to make sure that the shield of the
coax is properly bonded to the aluminum skin of the aircraft AT THE
ANTENNA (however you manage to do it), a copper counterpoint should not
be necessary. This could be as simple as using some light sanding to
bare metal at the proper bonding point. Once a good grounding bond is
achieved, the radiation performance between a copper counterpoise and an
aluminum counterpoise is very minor.
Just my 2 cents.
Mark Bitterlich
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Warren Hill
Sent: Wednesday, September 09, 2009 10:24 AM
Subject: Re: Yak-List: Re: CJ-6A comm antenna
Jim,
I'm sure that your radio guys mean well, but they're not be seeing the
whole picture.
The efficiency of a vertical radiator at VHF frequencies not only
depends on its length (which determines the resonant frequency), but
also the efficient transfer of power through the coax (RG-58 pretty
lossy at 120 MHz), the transfer of power from the coax to the antenna (a
non-refurbished Chinese PL-259 is low quality and an American one
doesn't mate well to the Chinese SO-239), the counterpoise (kinda like a
ground), it's angle (which influences the input impedance) and the
counterpoise conductivity (anodized aluminum is a poor choice).
With high quality coax (not the stuff that's normally available), a
copper counterpoise and the Chinese SO-239 / PL-259 connectors
refurbished, the resonant frequency for my CJ comm antenna is 124.82
MHz, around the center of the aviation band. The frequency range for an
acceptable SWR (standing wave ratio, which determines how much
transmitted power gets reflected back to the radio) is much broader than
any aviation wire antenna I've seen. This is because the width of the
radiating element also influences its bandwidth.
My take... getting this to work properly is simply way too much work for
a standard repair station with guys who are mostly trained to "assemble
and test." I've been working with antennas for more than 40 years. Set
up correctly, the CJ comm antenna works great.
All the best,
Warren Hill
Mesa, Arizona
On Sep 9, 2009, at 5:27 AM, cjpilot710@aol.com wrote:
> In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time,
> qas44n@yahoo.com
> writes:
>
> I wish I had known that a week ago. I just bought and installed a new
> one. :-(
>
> Anyway my local radio shop, told me that the Chinese antenna was a
> "little to long" for the frequency band and may have been the reason
> some guys were complaining of not hearing me to well over my Terra
> radios.
>
> Jim
>
>
> I have everything you need. I am restoring my CJ and getting rid of
> all the original comm equipment and radio nav gear. All the coax is
> un-cut, the Antenna is in good shape and the insulator is good to.
>
> Thanks
> Mike
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?
> p=262237#262237==============================================
> ================================================ -
> MATRONICS WEB FORUMS
> ================================================ - List
> Contribution Web Site sp;
> ==================================================
>
>
Message 9
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
Warren
Call me anytime after 4pm Central time
(832) 252-9298
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=262296#262296
Message 10
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
Mark,
Nice to hear the thoughts of a pilot and fellow radio amateur. Got my
ticket in 1964. While in graduate school I also ran an antenna
business where I designed and made VHF and UHF antennas... K7WX ;-).
As you know, at VHF frequencies small things matter in terms of
losses. A poorly done BNC connector at both ends of some bargain
basement coax with an oxidized connection between the airframe and the
outer conductor and the losses are significant. I agree that a good
connection between anodized aluminum would work, but these are old
airframes this can be difficult to maintain long-term. A copper
counterpoise could easily be considered more than is needed, but it's
100% dependable and requires no additional work after instillation.
Agreed. RG-142B/U is an elegant choice. I also like LMR-195 at these
frequencies. The dual outer shield is aluminum foil tape and a 90%
braid with a micro-cell foam dielectric. It's a little more flexible
and perhaps 1/3 the cost. Properly terminated, the losses for a 20 to
30 foot run at VHF frequencies for a 5 watt radio are very low.
Real world... Most of the work that we're doing involves distances
that are only a few miles apart, with typical signal strengths that
overcome many of the sins of a lossy antenna instillation. But for
trying to copy ATIS from way out, or tune that VOR from a significant
distance, I'll take the set-up with the lowest loss. Just my
preference after years of playing with all of this and trying to
maintain the original look of the CJ-6A.
Great stuff. Thanks for the thoughtful comments.
Warren Hill
On Sep 9, 2009, at 9:53 AM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
> Point, MALS-14 64E" <mark.bitterlich@navy.mil>
>
>
> Warren, concur on most of your comments. Obviously a fellow ham radio
> operator. Just some additional thoughts.
>
> The best replacement coax for RG-58 (with cost considerations) would
> likely be RG-142B/U ... Double shielded, silver coated, solid center
> conductor Teflon dielectric. Higher velocity factor than most others,
> (less loss) but somewhat less flexible. Failing that, RG-223. Same
> stuff, but with a polypropylene dielectric instead of Teflon.
> Standard
> .66 Vp. RG-142 is good up to over 1 GHz for short runs.
>
> I do not know CJ's at all, and possibly a better counterpoise is
> necessary, however I respectfully disagree that anodized aluminum is a
> poor choice. Anodized aluminum is used as a counterpoise on every
> commercial and most civilian aircraft in the world. Anodized aluminum
> is used to construct a wide variety of HF and UHF antennas (WA3JPY
> Warren :-) Concur that copper is a better choice, and silver
> would be
> even better than copper, but in the real world, I honestly offer that
> the difference in antenna performance between aluminum and copper is
> extremely small.
>
> The main problem when using anodized aluminum as the counterpoise to
> the
> 1/4 wavelength vertical is that you might not get a good electrical
> bond
> TO the actual aluminum because of the alodine used to cause the
> artificial corrosion method that is part of the anodizing process.
> This
> is why current military aircraft designs have gone to using AVDECK
> seals
> between the base of the antenna and the aircraft skin.
>
> Point being is that if you take care to make sure that the shield of
> the
> coax is properly bonded to the aluminum skin of the aircraft AT THE
> ANTENNA (however you manage to do it), a copper counterpoint should
> not
> be necessary. This could be as simple as using some light sanding to
> bare metal at the proper bonding point. Once a good grounding bond is
> achieved, the radiation performance between a copper counterpoise
> and an
> aluminum counterpoise is very minor.
>
> Just my 2 cents.
>
> Mark Bitterlich
>
>
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Warren Hill
> Sent: Wednesday, September 09, 2009 10:24 AM
> To: yak-list@matronics.com
> Subject: Re: Yak-List: Re: CJ-6A comm antenna
>
>
> Jim,
>
> I'm sure that your radio guys mean well, but they're not be seeing the
> whole picture.
>
> The efficiency of a vertical radiator at VHF frequencies not only
> depends on its length (which determines the resonant frequency), but
> also the efficient transfer of power through the coax (RG-58 pretty
> lossy at 120 MHz), the transfer of power from the coax to the
> antenna (a
> non-refurbished Chinese PL-259 is low quality and an American one
> doesn't mate well to the Chinese SO-239), the counterpoise (kinda
> like a
> ground), it's angle (which influences the input impedance) and the
> counterpoise conductivity (anodized aluminum is a poor choice).
>
> With high quality coax (not the stuff that's normally available), a
> copper counterpoise and the Chinese SO-239 / PL-259 connectors
> refurbished, the resonant frequency for my CJ comm antenna is 124.82
> MHz, around the center of the aviation band. The frequency range for
> an
> acceptable SWR (standing wave ratio, which determines how much
> transmitted power gets reflected back to the radio) is much broader
> than
> any aviation wire antenna I've seen. This is because the width of the
> radiating element also influences its bandwidth.
>
> My take... getting this to work properly is simply way too much work
> for
> a standard repair station with guys who are mostly trained to
> "assemble
> and test." I've been working with antennas for more than 40 years. Set
> up correctly, the CJ comm antenna works great.
>
> All the best,
>
> Warren Hill
> Mesa, Arizona
>
>
> On Sep 9, 2009, at 5:27 AM, cjpilot710@aol.com wrote:
>
>> In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time,
>> qas44n@yahoo.com
>> writes:
>>
>> I wish I had known that a week ago. I just bought and installed a
>> new
>
>> one. :-(
>>
>> Anyway my local radio shop, told me that the Chinese antenna was a
>> "little to long" for the frequency band and may have been the reason
>> some guys were complaining of not hearing me to well over my Terra
>> radios.
>>
>> Jim
>>
>>
>> I have everything you need. I am restoring my CJ and getting rid of
>> all the original comm equipment and radio nav gear. All the coax is
>> un-cut, the Antenna is in good shape and the insulator is good to.
>>
>> Thanks
>> Mike
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?
>> p=262237#262237==============================================
>> ================================================ -
>> MATRONICS WEB FORUMS
>> ================================================ - List
>> Contribution Web Site sp;
>> ==================================================
>>
>>
>>
>>
>>
>>
>>
>>
>
>
Message 11
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
Hi Warren,
Got my ticket in 1967, have worked with microwave and EW emitter antenna
designs myself for about the last 30 years or so, and have actually
participated in some antenna designs, but not at your level !!
Concur on all of your reply comments. Your observations concerning good
bonding between antennas and aluminum grounds is especially apt. This
is why we have gone to AVDECK seals and special dielectric grease on
most military models.
Nothing wrong with anyone who wants to go to the effort of installing
copper ground planes in their aircraft. I did not mean to imply there
was. It comes down to a personal decision really. I am a proponent of
making sure there is a good bond to an existing aluminum ground. It is
clearly arguable which method is best. Both will work, and your method
has definite merit! I guess it all depends on your point of view and
your personal experience.
Nothing wrong with LMR-195 either. Since most of our aircraft are
Experimental, the use of it is perfectly legit. However, coming from my
background, I tend to try and use hardware that is approved for use in
certificated aircraft, which is why I mentioned RG-142. It is the
preferred type, and in some cases (particularly with GPS systems) the
manufacturer will not honor your warranty if you use a substitute. On
our Yak and CJ model aircraft, we don't usually run coax lines
physically close to any high heat sources, but never-the-less, it needs
to be pointed out that any type of foam dielectric coax cable, while
increasing the velocity factor and also reducing the loss, also tends to
melt. Very easily. RG-142 simply will not do that. Another factor is
crush rating, or damage by stepping on it, etc., etc. You can pretty
much stand on RG-142 with very little (if any) damage, that can not be
said about foam dielectric coax types.
I mention all this not to argue, because when it comes down to how well
each type of transmission line will actually operate... As in, how well
the radio will transmit and receive, there is no question that LMR-195
will work as well or even better than other types INCLUDING RG-142! It
is cheap, it will work exceptionally well (if.. As you mentioned.. The
connectors are put on right) and will last a long time, as long as it is
not exposed to high heat, and it is protected from physical damage.
(FAA Avionics Repair Station guys will raise their eyebrows when they
see it in your airplane, but since it is Experimental, they can't say
much about it, and it will work well!!)
Take care,
Mark
-----Original Message-----
From: owner-yak-list-server@matronics.com
[mailto:owner-yak-list-server@matronics.com] On Behalf Of Warren Hill
Sent: Wednesday, September 09, 2009 3:09 PM
Subject: Re: Yak-List: Re: CJ-6A comm antenna
Mark,
Nice to hear the thoughts of a pilot and fellow radio amateur. Got my
ticket in 1964. While in graduate school I also ran an antenna business
where I designed and made VHF and UHF antennas... K7WX ;-).
As you know, at VHF frequencies small things matter in terms of losses.
A poorly done BNC connector at both ends of some bargain basement coax
with an oxidized connection between the airframe and the outer conductor
and the losses are significant. I agree that a good connection between
anodized aluminum would work, but these are old airframes this can be
difficult to maintain long-term. A copper counterpoise could easily be
considered more than is needed, but it's 100% dependable and requires no
additional work after instillation.
Agreed. RG-142B/U is an elegant choice. I also like LMR-195 at these
frequencies. The dual outer shield is aluminum foil tape and a 90% braid
with a micro-cell foam dielectric. It's a little more flexible and
perhaps 1/3 the cost. Properly terminated, the losses for a 20 to 30
foot run at VHF frequencies for a 5 watt radio are very low.
Real world... Most of the work that we're doing involves distances that
are only a few miles apart, with typical signal strengths that overcome
many of the sins of a lossy antenna instillation. But for trying to copy
ATIS from way out, or tune that VOR from a significant distance, I'll
take the set-up with the lowest loss. Just my preference after years of
playing with all of this and trying to maintain the original look of the
CJ-6A.
Great stuff. Thanks for the thoughtful comments.
Warren Hill
On Sep 9, 2009, at 9:53 AM, Bitterlich, Mark G CIV Det Cherry Point,
MALS-14 64E wrote:
> Point, MALS-14 64E" <mark.bitterlich@navy.mil>
>
>
> Warren, concur on most of your comments. Obviously a fellow ham radio
> operator. Just some additional thoughts.
>
> The best replacement coax for RG-58 (with cost considerations) would
> likely be RG-142B/U ... Double shielded, silver coated, solid center
> conductor Teflon dielectric. Higher velocity factor than most others,
> (less loss) but somewhat less flexible. Failing that, RG-223. Same
> stuff, but with a polypropylene dielectric instead of Teflon.
> Standard
> .66 Vp. RG-142 is good up to over 1 GHz for short runs.
>
> I do not know CJ's at all, and possibly a better counterpoise is
> necessary, however I respectfully disagree that anodized aluminum is a
> poor choice. Anodized aluminum is used as a counterpoise on every
> commercial and most civilian aircraft in the world. Anodized aluminum
> is used to construct a wide variety of HF and UHF antennas (WA3JPY
> Warren :-) Concur that copper is a better choice, and silver
> would be
> even better than copper, but in the real world, I honestly offer that
> the difference in antenna performance between aluminum and copper is
> extremely small.
>
> The main problem when using anodized aluminum as the counterpoise to
> the
> 1/4 wavelength vertical is that you might not get a good electrical
> bond
> TO the actual aluminum because of the alodine used to cause the
> artificial corrosion method that is part of the anodizing process.
> This
> is why current military aircraft designs have gone to using AVDECK
> seals
> between the base of the antenna and the aircraft skin.
>
> Point being is that if you take care to make sure that the shield of
> the
> coax is properly bonded to the aluminum skin of the aircraft AT THE
> ANTENNA (however you manage to do it), a copper counterpoint should
> not
> be necessary. This could be as simple as using some light sanding to
> bare metal at the proper bonding point. Once a good grounding bond is
> achieved, the radiation performance between a copper counterpoise
> and an
> aluminum counterpoise is very minor.
>
> Just my 2 cents.
>
> Mark Bitterlich
>
>
> -----Original Message-----
> From: owner-yak-list-server@matronics.com
> [mailto:owner-yak-list-server@matronics.com] On Behalf Of Warren Hill
> Sent: Wednesday, September 09, 2009 10:24 AM
> To: yak-list@matronics.com
> Subject: Re: Yak-List: Re: CJ-6A comm antenna
>
>
> Jim,
>
> I'm sure that your radio guys mean well, but they're not be seeing the
> whole picture.
>
> The efficiency of a vertical radiator at VHF frequencies not only
> depends on its length (which determines the resonant frequency), but
> also the efficient transfer of power through the coax (RG-58 pretty
> lossy at 120 MHz), the transfer of power from the coax to the
> antenna (a
> non-refurbished Chinese PL-259 is low quality and an American one
> doesn't mate well to the Chinese SO-239), the counterpoise (kinda
> like a
> ground), it's angle (which influences the input impedance) and the
> counterpoise conductivity (anodized aluminum is a poor choice).
>
> With high quality coax (not the stuff that's normally available), a
> copper counterpoise and the Chinese SO-239 / PL-259 connectors
> refurbished, the resonant frequency for my CJ comm antenna is 124.82
> MHz, around the center of the aviation band. The frequency range for
> an
> acceptable SWR (standing wave ratio, which determines how much
> transmitted power gets reflected back to the radio) is much broader
> than
> any aviation wire antenna I've seen. This is because the width of the
> radiating element also influences its bandwidth.
>
> My take... getting this to work properly is simply way too much work
> for
> a standard repair station with guys who are mostly trained to
> "assemble
> and test." I've been working with antennas for more than 40 years. Set
> up correctly, the CJ comm antenna works great.
>
> All the best,
>
> Warren Hill
> Mesa, Arizona
>
>
> On Sep 9, 2009, at 5:27 AM, cjpilot710@aol.com wrote:
>
>> In a message dated 9/9/2009 8:07:11 A.M. Eastern Daylight Time,
>> qas44n@yahoo.com
>> writes:
>>
>> I wish I had known that a week ago. I just bought and installed a
>> new
>
>> one. :-(
>>
>> Anyway my local radio shop, told me that the Chinese antenna was a
>> "little to long" for the frequency band and may have been the reason
>> some guys were complaining of not hearing me to well over my Terra
>> radios.
>>
>> Jim
>>
>>
>> I have everything you need. I am restoring my CJ and getting rid of
>> all the original comm equipment and radio nav gear. All the coax is
>> un-cut, the Antenna is in good shape and the insulator is good to.
>>
>> Thanks
>> Mike
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?
>> p=262237#262237==============================================
>> ================================================ -
>> MATRONICS WEB FORUMS
>> ================================================ - List
>> Contribution Web Site sp;
>> ==================================================
>>
>>
>>
>>
>>
>>
>>
>>
>
>
Message 12
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: CJ-6A comm antenna |
----- Original Message -----
From: "Warren Hill" <k7wx@earthlink.net>
Sent: Tuesday, September 08, 2009 10:46 PM
Subject: Yak-List: CJ-6A comm antenna
>
> Guys,
>
> Looking to buy several of the standard comm antennas the normally come
> with the CJ-6A. I know that many of you routinely take them off. Here is
> an opportunity to give yours a good home.
>
> If possible, looking for the entire assembly:
>
> Antenna.
> Bakelite (I think that's what it is) insulating / mounting plate.
> Intact female coax connector on underside.
> Nut plate.
>
> If you have one or more of the Chinese coaxial cable connectors, that
> would be a plus. The Chinese ones have a much coarser thread on the screw
> sleeve than the American PL-259.
>
> Refurbished, and with a suitable copper counterpoise, these antennas
> actually work very nicely with a very low SWR in the middle of the
> aviation band. Am doing a project for myself and several other CJ owners.
>
> Thanks,
>
> Warren Hill
> Mesa, AZ
>
> Warren.....contact me at mlbjr@earthlin.net off line.....I have one
> antenna. Marcus
>
>
>
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|